As Yale aims to bolster its reputation in the sciences, the University is dedicating more resources to improving science programs and facilities and recruiting talented science students and faculty. But at the same time, administrators said, science departments have seen a pattern of attrition among its undergraduate majors over the last decade.

Almost half the incoming freshmen who express interest in majoring in the sciences change their minds by senior year, administrators interviewed said. One science administrator said approximately 35 percent of each incoming freshman class is made up of prospective science majors — an average of 461 total students across eight years, based on data from the Office of Institutional Research. Yet the average number of science degrees awarded to those same eight classes has dwindled to an average of approximately 247 by graduation. This means that, on average, 46.5 percent of freshmen who are prospective science majors in each class switch to non-science majors by their senior year.

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Administrators offered multiple explanations for the attrition, from time-consuming coursework to simple logistics, and said they are addressing the issue by enhancing academic resources.

Dean of Undergraduate Science Education William Segraves said science attrition, especially at Yale, is not yet fully understood, and that he and other administrators hope to gather more information about the phenomenon in order to remedy it.

“A certain amount of changing of majors should be considered normal,” said Segraves. “But we want to be sure that it’s because a student discovered that her or his passion lay elsewhere, and not because we fell short in some way of doing what we needed to do to kindle and sustain her or his interest in science.”

But several students interviewed said they dropped their science majors after finding themselves unable to pursue other activities.

Cleo Handler ’12 said she entered Yale intending to be premed, having studied a variety of subjects in high school. As time wore on, though, she said she found that the heavy workload in the sciences and laboratory courses dominated her time, preventing her from pursuing some of her other interests, such as acting.

“I had always been interested in science,” Handler said in an e-mail Monday. “But I ended up feeling like it precluded me from doing all of the other things I loved.”

Handler’s experience is not uncommon: Several former science majors interviewed said they abandoned their intended science majors because they found the time commitment too demanding.

Frank Robinson, coordinator of the Science and QR Center, said classes like organic chemistry are often filled with pre-medical students, whom Robinson called a competitive, “high-powered lot.”

“Orgo has a tough reputation,” Robinson admitted.

Robinson, who oversees a program of more than 100 science and quantitative reasoning tutors, said demand for tutoring in chemistry went up by 50 percent in the 2008-’09 academic year. (He said the increase was likely due to a combination of more awareness of tutoring resources, as well as greater enrollment in chemistry courses.)

The tutoring program has been moderately successful, Robinson said, in that a students enrolled in year-long science courses, such as general physics or chemistry, and who have positive experiences with tutors during the first semesters, are likely to stick with both the classes and their tutors. And Segraves said he aims to expand tutoring support beyond what is currently offered, to combat some of the academic challenges science majors face.

In addition, Segraves said he has worked to accommodate upperclassmen interested in majoring in the sciences who would otherwise find it difficult to catch up. One possible reason for Yale’s science attrition, he said, is that while students in all academic areas often change their majors as they discover new interests, those students hoping to switch into the sciences are faced with numerous prerequisites.

Some of the changes, Segraves said, will be universal as new premedical requirements take effect in the near future. The American Association of Medical Colleges is currently working to revise premedical requirements, shifting them from a set of required courses to a checklist of skills. There will be less emphasis placed on taking certain courses such as organic chemistry, and greater emphasis on courses like biochemistry, which are more relevant to contemporary research.

“It’s expected that there will be some substantial changes in premedical requirements in the next few years, and I’m hopeful that those changes will have beneficial effects on science education,” Segraves said.

In addition, he said he is working to revamp science curricula, create new courses and expand undergraduate research opportunities. He also cited the Yale shuttle system and inconvenient class locations as logistical barriers to majoring in the sciences.

Still, Segraves cautioned that a student’s choice of major does not always indicate the range of his or her academic interests. For example, he said, there may be non-science majors who graduate intending to pursue a medical degree or doctorate.

Yale College Dean Mary Miller said many majors technically considered “non-science” have a scientific component, such as environmental studies, which she said is one of the fastest-growing majors.

“It’s important to remember that many students will take a robust course of study with many science courses while nevertheless not receiving a B.S.,” Miller said in an e-mail Monday. She added that many non-science majors — including her own advisees majoring in history of art or Latin American studies — also complete pre-medical requirements.

In the class of 2009, 248 students graduated with a degree in the sciences.